A file system is a method for storing and organizing computer data in which a file form is used to organize data stored in a memory and a file access policy is defined. Strictly speaking, the file system is a set of data management software implementing operations such as data storage, hierarchical data organization, and data access.
A conventional file system works in a kernel mode, while a user process runs in a user mode. If a process running in a user mode needs to access a file in a memory, for example, perform a read/write operation on the file, the process needs to execute a file system interface function. As executing the file system interface function belongs to a system call, the user mode is switched to a kernel mode. Then, the file system interface function is executed in the kernel mode to access the file in the memory. After file access is completed, the kernel mode is switched back to the user mode, and the process continues to run. The two switches between the user mode and the kernel mode consume resources and time.